The invention relates to a pressure control valve arrangement for controlling the fluid pressure in an ABS brake system of a vehicle in such a manner that, in the event of a tendency of individual wheels of the vehicle to lock, the brake pressure in associated brake cylinders can be adaptively adjusted. At least two diaphragm valves having diaphragms loaded by spring elements, and at least one electromagnetic control valve, which can be activated by an electronic control device and is intended for the pilot control of the diaphragm valves, are provided in a housing of the pressure control valve arrangement. The invention also relates to a method for producing the pressure control valve arrangement.
An ABS (antilock brake system) prevents locking of the wheels and enters into operation if a greater adhesion is required between a tire and the roadway than can be transmitted, i.e. if the driver overbrakes. In the event of overbraking, the central electronic control unit of the ABS brake system identifies, from rotational speed sensor signals, the tendency of one or more wheels to lock and calculates therefrom the activation of the pressure control valve arrangement acting on the associated brake cylinder. The brake pressure is then adjusted to optimum slip via the pressure control valve arrangement, which may be reduced, maintained or built-up in accordance with the wheel behavior and, therefore, the frictional conditions between tire and roadway.
A pressure control valve arrangement of the above-mentioned type for an ABS brake system is known from DE 101 56 773 A1. Single-channel pressure control valves with and without a relay action are generally used for ABS brake systems of vehicles. Pressure control valve arrangements with a relay action are used in semitrailers and drawbar trailers. ABS pressure control valve arrangements without a relay action, which is the area of concern in the present invention, are used in all other vehicles, for example in commercial vehicles, buses, semitrucks and also in trailers. Pressure control valve arrangements without a relay action have 3/2-way solenoid valves as pilot valves of diaphragm valves, an electronic control device activating the 3/2-way solenoid valves in order to be able to carry out the “pressure-maintaining”, “pressure-dissipating” and “pressure-building-up” functions necessary for ABS operation. During braking without response of the ABS (no tendency of a wheel to lock), the pressure medium, generally air, when ventilating and venting the brake cylinders, flows unobstructed through the pressure control valve arrangements in both directions. It is therefore ensured that the operation of the service brake system is not affected by the ABS pressure control valve arrangement.
There is therefore needed a pressure control valve arrangement that it is simpler to produce and install. At the same time, a corresponding method is needed for producing such a pressure control valve arrangement.
These and other needs are met by a pressure control valve arrangement, and a method of making the same, for controlling the fluid pressure in an ABS brake system of a vehicle such that, in the event of a tendency of individual wheels of the vehicle to lock, the brake pressure in associated brake cylinders can be adaptively adjusted, wherein at least two diaphragm valves having diaphragms loaded by spring elements, and at least one electromagnetic control valve, which can be activated by an electronic control device and is intended for the pilot control of the diaphragm valves, are provided in a housing of the pressure control valve arrangement. At least one valve seat of the at least one electromagnetic control valve is formed in a unipartite fashion with a housing part which is formed by a plastic injection-molded blank.
Advantageously, the valve seat does not need further machining and, after the primary forming together with the housing part, is then not machined further, for example by cutting, since the surface quality and roughness of an injection-molded plastic sufficiently meet the tightness requirements imposed on a valve seat of this type. The valve seat therefore does not need to be formed by inserts in the form of additional components, which results in an advantageous reduction in the number of components in the pressure control valve arrangement, and therefore the production and installation costs turn out to be advantageously lower.
According to particularly preferred embodiments, the housing part having the at least one valve seat is a plate-like, fiber-reinforced plastic injection-molded blank, wherein the housing part is composed, for example, of fiber-reinforced polyamide. A plastic of this type has a relatively high strength, stiffness and hardness, and is therefore suitable for the permanent loading necessary within the context of the ABS valve operation.
In particular, the at least one valve seat is formed on a surface of the housing part that faces another housing part in which the further components of the at least one electromagnetic control valve, such as an armature and a magnet core, are accommodated. A functional, electromagnetic control valve can then be obtained in a simple manner by the other housing part receiving the further components of the at least one electromagnetic control valve, such as the armature and the magnet core, being connected to the first housing part on which the valve seat is formed.
The other housing part receiving the further components of the at least one electromagnetic control valve, such as the armature and the magnet core, is preferably a plastic injection-molded blank into which at least one magnet coil of the electromagnetic control valve is injected. The measure further reduces the outlay on producing and installing the pressure control valve arrangement.
According to one development, the other housing part is provided with at least one passage bore for the insertion of the further components of the electromagnetic control valve, such as the armature and the magnet core, a center axis of the passage bore being arranged coaxially with respect to the valve seat. The at least one passage bore in the other housing part can then be closed by a cover.
On the basis of the above-described configuration of the components of the pressure control valve arrangement, the method for producing the latter then contains at least the following steps:
a) primary forming of one housing part of the housing as a plastic injection-molded blank together with at least one valve seat of the at least one electromagnetic control valve in a surface which faces the other housing part receiving the further components of the at least one electromagnetic control valve, such as an armature and a magnet core,
b) producing at least one passage bore in the other housing part of the housing for receiving the further components of the at least one electromagnetic control valve, a center axis of the passage bore being coaxial with the valve seat in the first housing part,
c) inserting the further components of the at least one electromagnetic control valve into the other housing part,
d) fastening the other housing part to the first housing part such that the at least one valve seat in the first housing part can interact with the further components of the at least one electromagnetic control valve, which components are arranged in the other housing part.
All of the main components of the electromagnetic control valve, such as the one housing part with the valve seat and the other housing part for receiving the further components of the electromagnetic control valve, such as the armature and the magnet core, can then be installed from a single installation direction, preferably vertically and from above, this having the advantage that there does not have to be a retooling operation during installation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.